John Lightfoot on Matthew 5:33

[It hath been said by them of old time, Thou shalt not forswear thyself, &c.] The law forbids perjury, Leviticus 19:12, &c. To which the Fathers of the Traditions reduced the whole sin of swearing, little caring for a rash oath. In this chapter of oaths they doubly sinned:

I. That they were nothing at all solicitous about an oath, so that what was sworn were not false. They do but little trouble themselves, what, how, how often, how rashly, you swear, so that what you swear be true.

In the Talmudic tract Shevuoth, and in like manner in Maimonides, oaths are distributed into these four ranks:

First, A promissory oath: when a man swore that he would do, or not do, this or that, &c. And this was one of the twofold oaths, which were also fourfold; that is, a negative or affirmative oath; and again, a negative or affirmative oath concerning something past, or a negative or affirmative oath concerning something to come: namely, when any one swears that he hath done this or that, or not done it; or that he will do this or that, or that he will not do it. "Whosoever, therefore, swears any of these four ways, and the thing is not as he swears, (for example, that he hath not cast a stone into the sea, when he hath cast it; that he hath cast it, when he hath not; that he will not eat, and yet eats; that he will eat, and yet eateth not,) behold, this is a false oath, or perjury."

"Whosoever swears that he will not eat, and yet eats some things which are not sufficiently fit to be eaten, this man is not guilty."

Secondly, A vain or a rash oath. This also is fourfold, but not in the same manner as the former: 1. When they asserted that with an oath which was contrary to most known truth; as, "If he should swear a man were a woman, a stone-pillar to be a pillar of gold," &c.; or when any swore that was or was not, which was altogether impossible; as, "that he saw a camel flying in the air." 2. When one asserted that by an oath, concerning which there was no reason that any should doubt. For example, that "Heaven is heaven, a stone is a stone," &c. 3. When a man swore that he would do that which was altogether impossible; namely, "that he would not sleep for three days and three nights; that he would taste nothing for a full week," &c. 4. When any swore that he would abstain from that which was commanded; as, "that he would not wear phylacteries," &c. These very examples are brought in the places alleged.

Thirdly, An oath concerning something left in trust: namely, when any swore concerning something left in trust with him, that it was stolen or broke or lost, and not embezzled by him, &c.

Fourthly, A testimonial oath, before a judge or magistrate.

In three of these kinds of swearing, care is taken only concerning the truth of the thing sworn, not of the vanity of swearing.

They seemed, indeed, to make some provision against a vain and rash oath: namely, 1. That he be beaten, who so swears, and become cursed: which Maimonides hints in the twelfth chapter of the tract alleged: with whom the Jerusalem Gemarists do agree; "He that swears two is two, let him be beaten for his vain oath." 2. They also added terror to it from fearful examples, such as that is in the very same place. "There were twenty-four assemblies in the south, and they were all destroyed for a vain oath." And in the same tract, a woman buried her son for an oath, &c. Yet they concluded vain oaths in so narrow a circle, that a man might swear a hundred thousand times, and yet not come within the limits of the caution concerning vain swearing.

II. It was customary and usual among them to swear by the creatures; "If any swear by heaven, by earth, by the sun, &c. although the mind of the swearer be under these words to swear by Him who created them, yet this is not an oath. Or if any swear by some of the prophets, or by some of the books of the Scripture, although the sense of the swearer be to swear by Him that sent that prophet, or that gave that book, nevertheless this is not an oath."

"If any adjure another by heaven or earth, he is not guilty."

They swore by Heaven. By Heaven so it is.

They swore by the Temple. "When turtles and young pigeons were sometimes sold at Jerusalem for a penny of gold, Rabban Simeon Ben Gamaliel said, By this habitation [that is, by this Temple] I will not rest this night, unless they be sold for a penny of silver."

"R. Zechariah Ben Ketsab said, By this Temple, the hand of the woman departed not out of my hand." "R. Jochanan said, By the Temple it is in our hand," &c.

"Bava Ben Buta swore by the Temple in the end of the tract Cherithuth, and Rabban Simeon Ben Gamaliel in the beginning; And so was the custom in Israel." Note this, "so was the custom."

They swore by the city Jerusalem. "R. Judah saith, He that saith, 'By Jerusalem,' saith nothing, unless with an intent purpose he shall vow towards Jerusalem." Where, also, after two lines coming between those forms of swearing and vowing are added, "Jerusalem, for Jerusalem, by Jerusalem. The Temple, for the Temple, by the Temple. The altar, for the altar, by the altar. The lamb, for the lamb, by the lamb. The chambers of the Temple, for the chambers of the Temple, by the chambers of the Temple. The wood, for the wood, by the wood. The sacrifices on fire, for the sacrifices on fire, by the sacrifices on fire. The dishes, for the dishes, by the dishes. By all these things, that I will do this to you."

They swore by their own heads. "One is bound to swear to his neighbour, and he saith, Vow (or swear) to me by the life of thy head," &c.